In this frame grab made from pool video, Dr. Conrad Murray listens as Judge Michael Pastor sentences him to the maximum four years in county jail for his involuntary manslaughter conviction of pop star Michael Jackson, Tuesday, Nov. 29, 2011 on Superior Court in Los Angeles. (AP Photo/Pool, CNN)

It wasn't the familiar voice of hits such as "Billie Jean" and "Thriller," but the slow, slurring recording of the singer that was found on his physician's cell phone that helped convince a judge to sentence the doctor to jail for four years.

The four-minute recording was one of the blockbuster revelations of Dr. Conrad Murray's involuntary manslaughter trial, a previously unknown piece of evidence that revealed an impaired Jackson describing his ambitions and aspirations as his personal physician listened.

It was also one of the trial's most haunting moments, and stuck in the mind of Superior Court Judge Michael Pastor as he considered in recent days how to sentence Murray for causing Jackson's unexpected death in June 2009. It wasn't the only thing the judge considered — he unwaveringly assailed the cardiologist's decisions and ethics for nearly 30 minutes on Tuesday — but helped convince Pastor to give Murray the maximum sentence.

Jurors unanimously convicted Murray on Nov. 7, but it was up to Pastor on Tuesday to sentence the doctor and explain his punishment.

"Of everything I heard and saw during the course of the trial, one aspect of the evidence stands out the most, and that is the surreptitious recording of Michael Jackson by his trusted doctor," Pastor said.

Murray's attorneys never explained in court why the recording was made, and prosecutors said they do not know what substances Jackson was under the influence of when the audio was recorded six weeks before his death. Murray had been giving the singer nightly doses of the anesthetic propofol to help him sleep.

The doctor's time in a Los Angeles jail will be automatically reduced to less than two years due to laws imposed due to California's prison overcrowding and budget woes.

Murray, 58, will have plenty of time if he wants to consider Pastor's harsh rebuke of him. The Houston-based cardiologist will be confined to a one-man cell and kept away from other prisoners.

With Jackson's family and Murray's mother and girlfriend looking on, the judge called the doctor's actions a "disgrace to the medical profession," and said he displayed a "failure of character" and had showed a complete lack of remorse for his significant role in causing Jackson's death.

"It should be made very clear that experimental medicine is not going to be tolerated, and Mr. Jackson was an experiment," Pastor said. "The fact that he participated in it does not excuse or lessen the blame of Dr. Murray, who simply could have walked away and said no as countless others did.

"But Dr. Murray was intrigued with the prospect of this money-for-medicine madness," the judge said.

Defense attorney J. Michael Flanagan said after the sentencing hearing that Murray made the recording accidentally while playing with a new application on his iPhone. He deleted it, but a computer investigator recovered it from the doctor's phone after Jackson's death.

Pastor said he believed the recording was made with more sinister intent.

"That tape recording was Dr. Murray's insurance policy," the judge said. "It was designed to record his patient surreptitiously; at that patient's most vulnerable point."

"I can't help but wonder if there had been some conflict between Michael Jackson and Dr. Murray at a later point in time in their relationship, what value would be placed on that tape recording, if the choice were to release that tape recording to a media organization to be used against Michael Jackson," Pastor said.

Pastor said Murray was motivated by a desire for "money, fame and prestige" and cared more about himself than Jackson.

After sentencing, Murray mouthed the words "I love you" to his mother and girlfriend in the courtroom. Murray's mother, Milta Rush, sat alone on a bench in the courthouse hallway.

"My son is not what they charged him to be," she said quietly. "He was a gentle child from the time he was small."

Of her son's future, she said, "God is in charge."

Jackson's family said in a statement read in court that they were not seeking revenge but a stiff sentence for Murray that would serve as a warning to opportunistic doctors.

"We're going to be a family. We're going to move forward. We're going to tour, play the music and miss him," brother Jermaine Jackson said.

Defense attorney Ed Chernoff implored Pastor to look at Murray's life and give him credit for a career of good works. "I do wonder whether the court considers the book of a man's life, not just one chapter," Chernoff said.

The judge responded: "I accept Mr. Chernoff's invitation to read the whole book of Dr. Murray's life. But I also read the book of Michael Jackson's life, including the sad final chapter of Dr. Murray's treatment of Michael Jackson."

A probation report released after sentencing said Murray was listed as suicidal and mentally disturbed in jail records before his sentencing. However, Murray's spokesman Mark Fierro said a defense attorney visited the cardiologist in jail last week and found him upbeat.

"That time is behind him," Fierro said.

What lies ahead for Murray is more flogging, with medical authorities in California, Nevada and Texas looking to strip his medical license and Jackson's father, Joseph, suing the physician for wrongful death.

Chernoff, who had advocated Murray receive probation instead of jail, said his client will forever live with the stigma of having caused Jackson's death.

"Whether Dr. Murray is a barista or a greeter at Walmart, he is still the man that killed Michael Jackson," he said.